Thesis (Ph.D.)--Ohio University, August, 2004. / Includes bibliographical references (p. 177-183)

Thesis (M.S.)--Ohio University, June, 2005. / Includes bibliographical references (p. 85-86)

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 81-86). Also available on the World Wide Web.

Thesis (Ph.D.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 177-183)

Thesis (M.S.)--Ohio University, June, 2005. / Title from PDF t.p. Includes bibliographical references (p. 85-86)

Thesis submitted in partial fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2015 / Space-borne GPS receivers designed for nano-satellites are faced with various challenges. This research is undertaken to address the problems of inefficiency and high-costs associated with space-borne GPS receivers. The problem of inefficiency relates to poor performances of the GPS receiver in terms of the algorithmic models, execution speed, memory usage and errors proness. The problem of high-costs relates to the spacegrade hardware cost, implementation complexity, development time, as well as the manufacturing, production and the testing processes involved. The research objectives are to i) establish an efficient high-dynamics software-defined GPS receiver, ii) demonstrate a firmware approach and then iii) postulate a low-cost hardware implementation roadmap. The research methodology employed to address the problems and to attain the objectives is based-on using Matlab computing platform to i) implement a software-defined GPS receiver using free open-source GPS receiver algorithms, ii) further develop the software GPS receiver and lastly iii) convert the improved GPS receiver algorithms to firmware. The GPS receiver was successfully implemented in Matlab floating-point algorithms with a ±100kHz Doppler search bins and was used to post-process a pre-captured real GPS L1 C/A signal dataset. The pre-captured GPS signal was acquired, tracked, decoded and post-processed to extract the navigation message; use to compute the GPS receiver position, UTC date and time. Attempt to convert the entire Matlab floating-point GPS receiver algorithms to equivalent VHDL implementations failed; however, three of the Matlab floating-point algorithms (check_t.m, deg2dms.m and findUtmZone.m), were successfully converted to equivalent fixed-point formats in Matlab, Simulink and finally VHDL. These three algorithms, now created and optimised to fixed-point formats (efficient and enable implementation unto a low-cost microcontroller), set the basis for the firmware implementation. They were simulated and verified in Matlab, Simulink and VHDL using the Matlab HDL Coder workflow. Altera Quartus II software was then used to compile (synthesise, place & route and generate programming files) the three converted generic VHDL algorithms to embedded firmware, suitable for a FPGA programming. The Matlab HDL Coder workflow used in this research is feasible and can be used to accurately design and implement an improved GPS receiver and furthermore achieve it in three equivalent algorithms. This conclusion was drawn and the proposed recommendations are to address the conversion issues in the other Matlab floating-point GPS receiver algorithms that failed in the conversion process and to further develop and implement the GPS receiver as a fully functional unit, based-on the Xilinx space-grade, radiation hardened and low-cost Virtex 5QV FPGA.

It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, mathematical equations were developed to estimate TEC over Sutherland (32.38⁰S, 20.81⁰E), during storm conditions, using the Empirical Orthogonal Function (EOF) analysis, combined with regression analysis. TEC was derived from GPS observations and a geomagnetic storm was defined for Dst ≤ -50 nT. The inputs for the model were chosen based on the factors that influence TEC variation, such as diurnal, seasonal, solar and geomagnetic activity variation, and these were represented by hour of the day, day number of the year, F10.7 and A index respectively. The EOF model was developed using GPS TEC data from 1999 to 2013 and tested on different storms. For the model validation (interpolation), three storms were chosen in 2000 (solar maximum period) and three others in 2006 (solar minimum period), while for extrapolation six storms including three in 2014 and three in 2015 were chosen. Before building the model, TEC values for the selected 2000 and 2006 storms were removed from the dataset used to construct the model in order to make the model validation independent on data. A comparison of the observed and modelled TEC showed that the EOF model works well for storms with non-significant ionospheric TEC response and storms that occurred during periods of low solar activity. High correlation coefficients between the observed and modelled TEC were obtained showing that the model covers most of the information contained in the observed TEC. Furthermore, it has been shown that the EOF model developed for a specific station may be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7⁰ and 10.6⁰ respectively. This is an important result as it reduces the data dimensionality problem for computational purposes. It may therefore not be necessary for regional storm-time TEC modelling to compute TEC data for all the closest GPS receiver stations since most of the needed information can be extracted from measurements at one location.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / There is an interest in using Global Positioning System (GPS) receivers to find: Time Space Position Information (TSPI), miss distances between a missile and target, and using the data real time as an independent tracking aid for range safety. Ashtech, Inc. has several standalone GPS receivers they believe can work at high g levels. This paper investigates how the Ashtech GPS receivers work under high g loading in one axis. The telemetry system used to collect data from the receivers and the reconstruction of the data will also be discussed. The test was done at SNORT (Supersonic Naval Ordnance Research Track) located at NAWS, China Lake, CA. The g level obtained was about +23 g’s with a deceleration of -15 g’s. The velocity reached was about Mach 2.0. A summary of the errors is included.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / NASA Marshall Space Flight Center’s Bantam Robust Guidance Navigation & Control Project is investigating off the shelf navigation sensors that may be inexpensively combined into Kalman filters specifically tuned for launch and orbital vehicles. For this purpose, Marshall has purchased several GPS receivers and is evaluating them for these applications. The paper will discuss the receiver selection criteria and the test equipment used for evaluation. An overview of the analysis will be presented including the evaluation used to determine their success or failure. It will conclude with goals of the program and a recommendation for all GPS users.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 19, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. C. Mark Cowell. Includes bibliographical references.